Erik J. Ragsdale* and James G. Baldwin
-Author Affiliations
Department of Nematology, University of California, Riverside, CA 92521, USA
*Author for correspondence (erik.ragsdale@email.ucr.edu).
Abstract
Modern morphology-based systematics, including questions of incongruence with molecular data, emphasizes analysis over similarity criteria to assess homology. Yet detailed examination of a few key characters, using new tools and processes such as computerized, three-dimensional ultrastructural reconstruction of cell complexes, can resolve apparent incongruence by re-examining primary homologies. In nematodes of Tylenchomorpha, a parasitic feeding phenotype is thus reconciled with immediate free-living outgroups. Closer inspection of morphology reveals phenotypes congruent with molecular-based phylogeny and points to a new locus of homology in mouthparts. In nematode models, the study of individually homologous cells reveals a conserved modality of evolution among dissimilar feeding apparati adapted to divergent lifestyles. Conservatism of cellular components, consistent with that of other body systems, allows meaningful comparative morphology in difficult groups of microscopic organisms. The advent of phylogenomics is synergistic with morphology in systematics, providing an honest test of homology in the evolution of phenotype.
Caenorhabditis elegans comparative morphology evolution of novelty congruence plant parasitism
systematics
Footnotes
Received December 7, 2009.
Accepted January 6, 2010.
© 2010 The Royal Society
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